This invention relates to the field of metallurgy, and particularly to the field of processing precipitation hardenable aluminum alloys.
A fine grain structure tends to improve the formability of aluminum alloys and allows them to be formed under superplastic conditions. However, grain refinement is difficult to achieve in aluminum alloys, and attempts to obtain a fine grain structure by conventional mechanical working and heating have resulted in the material recrystallizing to the original coarse grain structure.
U.S. Pat. No. 4,092,181 to Paton and Hamilton describes a method of imparting a fine grain structure to precipitation hardening aluminum alloys. The present invention is an improvement of the earlier patented method in that it describes additional features which are useful in obtaining a fine grain structure under certain production conditions.